8307955: Prefer to PTRACE_GETREGSET instead of PTRACE_GETREGS in meth…

…od 'ps_proc.c::process_get_lwp_regs'

Reviewed-by: cjplummer, kevinw

src/jdk.hotspot.agent/linux/native/libsaproc/ps_proc.c

@@ -125,10 +125,6 @@ static bool process_write_data(struct ps_prochandle* ph,
 static bool process_get_lwp_regs(struct ps_prochandle* ph, pid_t pid, struct user_regs_struct *user) {
   // we have already attached to all thread 'pid's, just use ptrace call
   // to get regset now. Note that we don't cache regset upfront for processes.
-// Linux on x86 and sparc are different.  On x86 ptrace(PTRACE_GETREGS, ...)
-// uses pointer from 4th argument and ignores 3rd argument.  On sparc it uses
-// pointer from 3rd argument and ignores 4th argument
-#define ptrace_getregs(request, pid, addr, data) ptrace(request, pid, data, addr)
 
 #if defined(_LP64) && defined(PTRACE_GETREGS64)
 #define PTRACE_GETREGS_REQ PTRACE_GETREGS64
@@ -138,22 +134,22 @@ static bool process_get_lwp_regs(struct ps_prochandle* ph, pid_t pid, struct use
 #define PTRACE_GETREGS_REQ PT_GETREGS
 #endif
 
-#ifdef PTRACE_GETREGS_REQ
- if (ptrace_getregs(PTRACE_GETREGS_REQ, pid, user, NULL) < 0) {
+#if defined(PTRACE_GETREGSET)
+  struct iovec iov;
+  iov.iov_base = user;
+  iov.iov_len = sizeof(*user);
+  if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, (void*) &iov) < 0) {
+    print_debug("ptrace(PTRACE_GETREGSET, ...) failed for lwp %d\n", pid);
+    return false;
+  }
+  return true;
+#elif defined(PTRACE_GETREGS_REQ)
+ if (ptrace(PTRACE_GETREGS_REQ, pid, NULL, user) < 0) {
    print_debug("ptrace(PTRACE_GETREGS, ...) failed for lwp(%d) errno(%d) \"%s\"\n", pid,
                errno, strerror(errno));
    return false;
  }
  return true;
-#elif defined(PTRACE_GETREGSET)
- struct iovec iov;
- iov.iov_base = user;
- iov.iov_len = sizeof(*user);
- if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, (void*) &iov) < 0) {
-   print_debug("ptrace(PTRACE_GETREGSET, ...) failed for lwp %d\n", pid);
-   return false;
- }
- return true;
 #else
  print_debug("ptrace(PTRACE_GETREGS, ...) not supported\n");
  return false;